The present invention relates to optical coupling devices for connecting an optical fiber to another optical fiber, for connecting an optical fiber to a light-emitting element, photoconductive element or like semiconductor, and for connecting an optical fiber or a semiconductor element to a slab-type optical waveguide path formed on a substrate so that light can be propagated between the two members connected together. The invention also relates to a method of fabricating such devices.
Two optical elements are optically connected together usually by holding them in contact with each other at their surfaces to be coupled together, with their optical axes in alignment, and fixing the elements in place with an adhesive, or by spacing the two elements apart by a small clearance and filling the clearance with a transparent resin. However, such methods generally involve extreme difficulty in accurately aligning the optical axes of the two elements to be coupled together and are low in coupling efficiency. Further because heat-resistant adhesives are almost unavailable, the use of the adhesive entails the problem that when the optically coupled elements are used at high temperatures, the adhesive usually deteriorates early, permitting misalignment of the optical axes or resulting in a lower coupling efficiency. The device wherein resin is used for coupling has the drawback that the resin is expanded or contracted by changes in temperature to create variations in coupling efficiency.